1. Field of the Invention
The present disclosure relates to lubrication systems, and more particularly to lubricant scavenging systems for gas turbine engines.
2. Description of Related Art
Conventional gas turbine engines typically include a low pressure spool (including a low pressure compressor and a low pressure turbine coupled by a low pressure shaft) and a high pressure spool (including a high pressure compressor and a high pressure turbine coupled by a high pressure shaft). Some gas turbine engines include separate fan disc shaft coupled to the low speed shaft by a gearbox for rotating the fan disc at a different speed than the low pressure spool. The shafts are rotatably supported by bearings housed in bearing compartments where contacting portions of the shafts and bearings are lubricated and cooled by a flow of lubricating liquid transiting the bearings. After transiting the bearings, lubricant exits the bearing compartment through a scavenging system for filtering and cooling before being returned to the bearing compartment.
Shaft seals bounding the bearing compartment couple the shaft to the bearing compartment. This seals the bearing compartment from the environment external to the compartment, confining lubricant to the bearing compartment interior, at the expense of parasitic losses such as from friction between the shaft seal and shaft surface. The amount of parasitic loss is a function of differential pressure across the shaft seals. Differential pressure in turn depends on the pressure within the bearing compartment in comparison to pressure on the shaft seal exterior. Since the exterior pressure can change during engine operation, e.g. increasing with shaft speed for example, parasitic losses typically increase in conventional gas turbine engine architectures with shaft speed.
Conventional gas turbine engine lubrication systems have generally been satisfactory for their intended purpose. However, there is a need for gas turbine engines with improved engine efficiency, such as through reduced parasitic loss from at interfaces between rotating components and shaft seals at high rotor speeds. The present disclosure provides solutions to these needs.